In an earlier U.S. Pat. No. 4,007,454, issued to Charles Cain et al, there is disclosed the technique for generating and using what is referred to as a "rotating electric field" in a device for remotely measuring the orientation of a meter hand or other rotating object. Further testing and analysis has shown that the theory of operation of the invention of the aforementioned Cain et al patent is clarified by considering that the portion of the field which is generated in the space adjacent the meter hand or other rotating object to be monitored is such that the resultant vector representing maximum strength of the electric field rotates, by which means the effect of a "rotating electric field" is approximated or approached.
In the Cain et al apparatus mentioned hereinabove there is described a circular array of electrodes with a detecting electrode located at the center of and coplanar with the array. By applying the successive phases of a polyphase voltage to successive electrodes in the circular array, the maximum field strength vector is thus caused to effectively rotate in the adjacent space to accomplish this rotating effect of the maximum field strength vector. Diametrically opposite pairs of the aforementioned electrodes are connected to successive phases of a polyphase voltage source in such a manner as to produce the rotating effect of the maximum field strength vector.
Various changes and modifications have been made to this basic invention as disclosed in U.S. Pat. No. 4,007,454. For example, one such change is disclosed in U.S. patent application Ser. No. 728,116, filed Sept. 30, 1976, still pending. In the aforementioned application the shape of the electrodes themselves are changed. Tests have shown that this gives an improved output linearity to the arrangement. Another improvement is the subject of U.S. Pat. No. 4,214,152, issued July 22, 1980, in which there is an interdial error correction technique introduced to the circuitry thereof.
Even with these improvements there exist certain problems in the generation and use of the electric field. By "polyphase" it is meant that each signal lags behind its neighbor somewhat. The earlier teachings referenced above have utilized six sine waves separated in phase by 60.degree.. With the sine wave each drive signal rises and falls smoothly as time progresses.